Collating devices for confirming whether or not an object to be processed or an object to be detected is correct, contamination detecting devices, and position detecting devices for controlling positioning are used in detection devices in products and various types of manufacturing equipment for semiconductors and the like.
In these devices, a method is used that is based upon a correlation between images (data). For example, the method is based on the correlation between, for example, an image that has been taken in advance and stored or recorded into memory or the like (hereinafter termed the “stored image”) and an image that has been taken as being the subject of collation to the stored image (hereinafter termed the “collation image”).
As typical methods that uses correlation, there is a method based on a normalized correlation function, and a method known as the “phase-only correlation method.” An example of a pattern collating device that uses the phase-only correlation method is given in Japanese Patent 3930067 (“JP '067”). The phase-only correlation method is used in position detection.
In the phase-only correlation method, both a stored image pattern and, for example, a collation image pattern are subjected to discrete Fourier transforms, and the phase components are extracted while causing all of the amplitudes of the pattern of the individual phase components obtained thereby to be equal to 1. Patterns of the extracted phase components are then composited respectively for the stored image and the collation image, and the composited patterns are subjected to an inverse discrete Fourier transform to obtain a correlation pattern. The image collating and position detection is performed based on the correlation pattern obtained in this way.
The phase-only correlation method, as implied by the name, obtains a correlation pattern that is limited to the information of the phase components, to obtain a strong correlation even if there is some degree of variation in the imaging conditions, such as the light source, or the like. Because of this, when compared to methods based on normalized correlation functions, the phase-only correlation method is known for its high detection sensitivity in collating and high resolution in position detection.
Japanese Unexamined Patent Application Publication 2007-78511 (“JP '511”), for example, describes a method that is an improvement of the phase-only correlation method. In this method, the effect of noise is reduced using frequency weighting based on spatial frequency information in the stored image.
However, in “JP '067”, no mention or thought is given to the case wherein the accuracy of the image collating or position detection suffers as a result of the inclusion of noise that is common to both images, known as “fixed pattern noise,” such as in the case wherein the stored image and the collation image were imaged by the same image capturing device. “JP '511” has, as the object thereof, reliable collation even when there is some degree of included noise; however, there is insufficient thought given to the properties of the fixed pattern noise, and the effectiveness when fixed pattern noise is included in the images is limited.
One of the objects of the present invention is to enable an improvement in the accuracy of pattern collating and position detection.
Note that there is no limitation to the aforementioned object, and, as another object of the present invention, there is the ability to perform positioning, which is an effect of the operation brought about by the various structures disclosed in the forms for embodying the present invention, described above, effects of operation that cannot be provided through the conventional technology.